Diffusion transfer photographic products and processes are known to the art and details relating thereto can be found in U.S. Pat. Nos. 2,983,606; 3,415,644; 3,415,645; 3,415,646; 3,473,925; 3,482,972; 3,551,406; 3,573,042; 3,573,043; 3,573,044; 3,576,625; 3,576,626; 3,578,540; 3,569,333; 3,579,333; 3,594,164; 3,594,165; 3,597,200; 3,647,437; 3,672,486; 3,672,890; 3,705,184; 3,752,836; 3,857,865, all of which are incorporated here in their entirety. Essentially, diffusion transfer photographic products and processes involve film units having a photosensitive system including at least one silver halide layer, usually integrated with an image-providing material. After photoexposure, the photosensitive system is developed to establish an imagewise distribution of a diffusible image-providing material, at least a portion of which is transferred by diffusion to an image-receiving layer capable of mordanting or otherwise fixing the transferred image-providing material. In some diffusion transfer products, the transfer image is viewed by reflection after separation of the image-receiving element from the photosensitive system. In other products, however, such separation is not required and instead the transfer image-receiving layer is viewed against the reflecting background usually provided by a dispersion of a white reflecting pigment, such as, for example, titanium dioxide. The latter type of film unit is generally referred to in the art as integral negative-positive film units and are described, for example, in the above-mentioned U.S. Pat. Nos. 3,415,644 and 3,594,165.
U.S. Pat. No. 3,362,819, issued Jan. 9, 1968, teaches image-receiving elements particularly adapted for use in the above-described diffusion transfer processes which comprise a support carrying on one surface thereof, in sequence, a polymeric acid layer, preferably an inert timing or spacer layer, and an image-receiving layer adapted to provide a visible image upon transfer to said image-receiving layer of diffusible dye image-forming substance.
Additional details relating to photographic diffusion transfer processes, elements and film units may be found in Research Disclosure, November 1976, No. 15162.
It is known that exposed photographic film units, including diffusion transfer photographic film units may be processed by so-called web processing wherein the photographic reagents are carried to the exposed film units by means of a web or pod. Examples of such processes will be described in the following patents.
U.S. Pat. No. 3,615,482, issued Oct. 26, 1971 is directed to a gellable photoprocessing composition comprising an aqueous photoprocessing solution and a reversible gel-former selected from a carrageneen, furcellarans and combinations thereof. The gellable compositions are employed in a process which comprises heating the gellable composition; contacting a photosensitive medium with the heated gellable composition; cooling the processing composition to a temperature below its setting temperature to form a gelled processing composition and then removing the gelled processing composition from the photosensitive medium.
British Pat. No. 1,121,277, published July 24, 1968, is directed to a method for developing an exposed silver halide emulsion which comprises contacting the emulsion layer with a substantially dry-to-the-touch medium comprising a support sheet and a gelled coating on the support sheet including a colloid binder and various photoprocessing materials. Upon the application of heat to the dry-to-the-touch medium, water is releasable therefrom and activates a silver halide developing agent associated with the emulsion. It is also taught that the processing medium itself can serve as the image-receiving layer.
U.S. Pat. No. 2,558,857, issued July 3, 1951, is directed to a photographic developer element comprising a support carrying an image-receiving layer and a layer of viscous processing composition. The viscous processing composition receives its viscosity from a film-forming material such as sodium alginate, hydroxyethyl cellulose and the like. The photographic developer element is contacted with an exposed photosensitive element so that the viscous layer of processing materials contacts the photosensitive element. The viscous processing composition permeates into the exposed photosensitive element developing the latent image therein and soluble silver complexes transfer to the image-receiving layer. The photographic developer element which now contains the developed silver image is then separated from the photosensitive element.
U.S. Pat. No. 3,907,563, issued Sept. 23, 1975, is directed to a diffusion transfer process wherein the image-receiving element is impregnated with a photographic processing liquid. A photosensitive element having dye image-providing materials associated therewith is exposed and then laminated to the described image-receiving element. The processing composition retained in the image-receiving element will diffuse to the photosensitive element developing the latent image contained therein and providing for the imagewise transfer of dye to the image-receiving layer. The image-receiving layer and photosensitive element are maintained as an integral unit.
Other patents which disclose photographic processing composition in association with image-receiving layers include, for example, U.S. Pat. Nos. 2,572,357, issued Oct. 23, 1951; 2,616,804, issued Nov. 4, 1952; and 3,345,165, issued Oct. 3, 1967.